U.S. patent application number 15/235542 was filed with the patent office on 2016-12-01 for rotatable frame, lithographic apparatus, projection system, method for focusing radiation and device manufacturing method.
This patent application is currently assigned to ASML Netherlands B.V.. The applicant listed for this patent is ASML Netherlands B.V.. Invention is credited to Ruud Antonius Catharina Maria BEERENS, Arno Jan BLEEKER, Theodorus Petrus Maria CADEE, Thomas Josephus Maria CASTENMILLER, Pieter Willem Herman DEJAGER, Heine Melle MULDER, Danny Maria Hubertus PHILIPS, Roger Anton Marie TIMMERMANS, Koen Jacobus Johannes ZAAL.
Application Number | 20160349628 15/235542 |
Document ID | / |
Family ID | 47683714 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160349628 |
Kind Code |
A1 |
BLEEKER; Arno Jan ; et
al. |
December 1, 2016 |
ROTATABLE FRAME, LITHOGRAPHIC APPARATUS, PROJECTION SYSTEM, METHOD
FOR FOCUSING RADIATION AND DEVICE MANUFACTURING METHOD
Abstract
A projection system, configured to project a radiation beam onto
a target, includes a rotatable frame configured to rotate about an
axis defining a tangential direction and a radial direction,
wherein the rotatable frame holds a lens configured to focus the
radiation beam in only the tangential or radial direction; and a
stationary part comprising a substantially stationary lens
configured to focus the radiation beam in only the other of the
tangential or radial direction.
Inventors: |
BLEEKER; Arno Jan;
(Westerhoven, NL) ; CASTENMILLER; Thomas Josephus
Maria; (Eindhoven, NL) ; DEJAGER; Pieter Willem
Herman; (Middelbeers, NL) ; MULDER; Heine Melle;
(Veldhoven, NL) ; ZAAL; Koen Jacobus Johannes;
(Eindhoven, NL) ; CADEE; Theodorus Petrus Maria;
(Asten, NL) ; PHILIPS; Danny Maria Hubertus; (Son
en Breugel, NL) ; BEERENS; Ruud Antonius Catharina
Maria; (Roggel, NL) ; TIMMERMANS; Roger Anton
Marie; (Nederweert, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASML Netherlands B.V. |
Veldhoven |
|
NL |
|
|
Assignee: |
ASML Netherlands B.V.
Veldhoven
NL
|
Family ID: |
47683714 |
Appl. No.: |
15/235542 |
Filed: |
August 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14382228 |
Aug 29, 2014 |
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PCT/EP2013/051800 |
Jan 30, 2013 |
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15235542 |
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61622922 |
Apr 11, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/70383 20130101;
G03F 7/70425 20130101; G03F 7/70366 20130101; G03F 7/70291
20130101; G03F 7/70475 20130101; G03F 7/20 20130101; G03F 7/704
20130101; G03F 7/70716 20130101; G03F 7/70275 20130101; G03F
7/70075 20130101; G03F 7/70391 20130101; G03F 7/7005 20130101 |
International
Class: |
G03F 7/20 20060101
G03F007/20 |
Claims
1. A rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein the
flange is positioned between an upper section and a lower section
of the shaft, wherein the upper section and the lower section are
configured such that, during rotation, a moment exerted on the
flange by the upper section opposes and substantially equals a
moment exerted on the flange by the lower section.
2. The frame of claim 1, wherein a cross-section of the upper
section is different from a cross-section of the lower section.
3. The frame of claim 1, wherein a cross-section of the upper
section corresponds to a cross-section of the lower section.
4. The frame of claim 1, wherein the shaft exerts substantially no
moment on the flange about a second axis perpendicular to the
axis.
5. The frame of claim 1, wherein the angle at which the flange
extends is substantially constant over a continuous range of
rotation speeds.
6. The frame of claim 5, wherein the continuous range of rotation
speeds has a lower limit of 0 and an upper limit of 200 Hz.
7. The frame of claim 1, further comprising a second flange
configured to hold a second lens, wherein the second flange extends
radially outwards at a second angle relative to the axis.
8. The frame of claim 1, wherein the shaft has a smaller radius
than the flange.
9. The frame of claim 1, wherein, during rotation, the lower
section of the shaft is configured to tilt about an annulus
extending around the axis on the shaft.
10. The frame of claim 1, further comprising an actuator or a
bearing disposed within a recess adjacent to the shaft and along
the axis.
11. A rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein, during
rotation, a section of the shaft on one side, in the axial
direction, of the flange exerts substantially no moment on the
flange.
12. The frame of claim 11, wherein: the flange has an inner edge a
distance R.sub.0 from the axis and an outer edge a distance R.sub.1
from the axis, and a section of the shaft adjacent to the flange
has an inner edge a distance R.sub.2 from the axis and an outer
edge a distance R.sub.3 from the axis, and a product of R.sub.0 and
R.sub.1 differs from a product of R.sub.2 and R.sub.3 by at most
10%.
13. The frame of claim 12, wherein the product of R.sub.0 and
R.sub.1 is substantially equal to the product of R.sub.2 and
R.sub.3.
14. The frame of claim 12, wherein R.sub.1 is substantially equal
to R.sub.3.
15. The frame of claim 11, wherein the shaft has a smaller radius
than the flange.
16. The frame of claim 11, wherein the angle at which the flange
extends is substantially constant over a continuous range of
rotation speeds.
17. The frame of claim 16, wherein the continuous range of rotation
speeds has a lower limit of 0 and an upper limit of 140 Hz.
Description
[0001] This application incorporates by reference in their
entireties U.S. patent application Ser. No. 14/382,228, filed Aug.
29, 2014, International Application No. PCT/EP2013/051800, filed
Jan. 30, 2013 and U.S. provisional application 61/622,922, filed
Apr. 11, 2012.
FIELD
[0002] The present invention relates to a rotatable frame, a
lithographic apparatus, a projection system, a method for focusing
radiation and a device manufacturing method.
BACKGROUND
[0003] A lithographic or exposure apparatus is a machine that
applies a desired pattern onto a substrate or part of a substrate.
The apparatus may be used, for example, in the manufacture of
integrated circuits (ICs), flat panel displays and other devices or
structures having fine features. In a conventional lithographic or
exposure apparatus, a patterning device, which may be referred to
as a mask or a reticle, may be used to generate a circuit pattern
corresponding to an individual layer of the IC, flat panel display,
or other device). This pattern may transferred on (part of) the
substrate (e.g. silicon wafer or a glass plate), e.g. via imaging
onto a layer of radiation-sensitive material (resist) provided on
the substrate.
[0004] Instead of a circuit pattern, the patterning device may be
used to generate other patterns, for example a color filter
pattern, or a matrix of dots. Instead of a conventional mask, the
patterning device may comprise a patterning array that comprises an
array of individually controllable elements that generate the
circuit or other applicable pattern. An advantage of such a
"maskless" system compared to a conventional mask-based system is
that the pattern can be provided and/or changed more quickly and
for less cost.
[0005] Thus, a maskless system includes a programmable patterning
device (e.g., a spatial light modulator, a contrast device, etc.).
The programmable patterning device is programmed (e.g.,
electronically or optically) to form the desired patterned beam
using the array of individually controllable elements. Types of
programmable patterning devices include micro-mirror arrays, liquid
crystal display (LCD) arrays, grating light valve arrays, arrays of
self-emissive contrast devices and the like. A programmable
patterning device could also be formed from an electro-optical
deflector, configured for example to move spots of radiation
projected onto a target (e.g., the substrate) or to intermittently
direct a radiation beam away from the target (e.g., the substrate),
for example to a radiation beam absorber. In either such
arrangement, the radiation beam may be continuous.
SUMMARY
[0006] A maskless lithographic or exposure apparatus may be
provided with, for example, an optical column capable of creating a
pattern on a target portion of a substrate. The optical column may
be provided with a self emissive contrast device configured to emit
a beam and a projection system configured to project at least a
portion of the beam onto a target. The apparatus may be provided
with an actuator to move the optical column or a part thereof with
respect to the substrate. By, for example, movement of the optical
column or a part thereof, the beam may be moved with respect to the
substrate. By switching "on" or "off" the self-emissive contrast
device during the movement of the beam, a pattern on the substrate
may be created.
[0007] It is desirable, for example, to improve the accuracy of
printing radiation beams onto a target (e.g., of a substrate).
[0008] According to an embodiment of the invention, there is
provided a rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein the
flange is positioned between an upper section and a lower section
of the shaft, wherein the upper section and the lower section are
configured such that during rotation a moment exerted on the flange
by the upper section opposes and substantially equals a moment
exerted on the flange by the lower section.
[0009] According to an embodiment of the invention, there is
provided a rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein during
rotation a section of the shaft on one side, in the axial
direction, of the flange exerts substantially no moment on the
flange.
[0010] According to an embodiment of the invention, there is
provided a rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein the
flange comprises a recess or a protruding rim on a surface of the
flange that faces the middle, in the axial direction, of the
shaft.
[0011] According to an embodiment of the invention, there is
provided a rotatable frame, for use in a lithographic apparatus,
configured to rotate about an axis, the rotatable frame comprising:
a shaft; and a flange extending radially outwards at an angle
relative to the axis and configured to hold a lens, wherein the
flange is connected to the shaft by a connector that is more
flexible that the flange.
[0012] According to an embodiment of the invention, there is
provided a projection system, configured to project a radiation
beam onto a target, comprising: a rotatable frame configured to
rotate about an axis defining a tangential direction and a radial
direction, wherein the rotatable frame holds a lens configured to
focus the radiation beam in only the tangential or radial
direction; and a stationary part comprising a substantially
stationary lens configured to focus the radiation beam in only the
other of the tangential or radial direction.
[0013] According to an embodiment of the invention, there is
provided a method of focusing a radiation beam onto a target using
a lithographic apparatus, the method comprising: focusing the
radiation beam in only a tangential direction or a radial direction
of a rotatable frame configured to rotate about an axis with a lens
held by the rotatable frame; and focusing the radiation beam in
only the other of the tangential direction or the radial direction
by a substantially stationary lens.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying schematic
drawings in which corresponding reference symbols indicate
corresponding parts, and in which:
[0015] FIG. 1 depicts a part of a lithographic or exposure
apparatus according to an embodiment of the invention;
[0016] FIG. 2 depicts a top view of a part of the apparatus of FIG.
1 according to an embodiment of the invention;
[0017] FIG. 3 depicts a highly schematic, perspective view of a
part of a lithographic or exposure apparatus according to an
embodiment of the invention;
[0018] FIG. 4 depicts a schematic top view of projections by the
apparatus according to FIG. 3 onto a target according to an
embodiment of the invention;
[0019] FIG. 5 depicts in cross-section, a part of an embodiment of
the invention;
[0020] FIG. 6 depicts schematically a rotatable frame according to
an embodiment of the invention;
[0021] FIG. 7 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0022] FIG. 8 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0023] FIG. 9 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0024] FIG. 10 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0025] FIG. 11 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0026] FIG. 12 depicts schematically part of a rotatable frame
according to an embodiment of the invention;
[0027] FIG. 13 depicts schematically part of a projection system
according to an embodiment of the invention;
[0028] FIG. 14 depicts schematically part of a projection system
according to an embodiment of the invention;
[0029] FIG. 15 depicts schematically part of a projection system
according to an embodiment of the invention;
[0030] FIG. 16 depicts schematically part of a projection system
according to an embodiment of the invention;
[0031] FIG. 17 depicts schematically part of a projection system
according to an embodiment of the invention;
[0032] FIG. 18 depicts schematically part of a projection system
according to an embodiment of the invention;
[0033] FIG. 19 depicts schematically part of a projection system
according to an embodiment of the invention; and
[0034] FIG. 20 depicts schematically part of a rotatable frame
according to an embodiment of the invention.
DETAILED DESCRIPTION
[0035] An embodiment of the present invention relates to an
apparatus that may include a programmable patterning device that
may, for example, be comprised of an array or arrays of
self-emissive contrast devices. Further information regarding such
an apparatus may be found in PCT patent application publication no.
WO 2010/032224 A2, U.S. patent application publication no. US
2011-0188016, U.S. patent application no. U.S. 61/473,636 and U.S.
patent application No. 61/524,190 which are hereby incorporated by
reference in their entireties. An embodiment of the present
invention, however, may be used with any form of programmable
patterning device including, for example, those discussed
above.
[0036] FIG. 1 schematically depicts a schematic cross-sectional
side view of a part of a lithographic or exposure apparatus. In
this embodiment, the apparatus has individually controllable
elements substantially stationary in the X-Y plane as discussed
further below although it need not be the case. The apparatus 1
comprises a substrate table 2 to hold a substrate, and a
positioning device 3 to move the substrate table 2 in up to 6
degrees of freedom. The substrate may be a resist-coated substrate.
In an embodiment, the substrate is a wafer. In an embodiment, the
substrate is a polygonal (e.g. rectangular) substrate. In an
embodiment, the substrate is a glass plate. In an embodiment, the
substrate is a plastic substrate. In an embodiment, the substrate
is a foil. In an embodiment, the apparatus is suitable for
roll-to-roll manufacturing.
[0037] The apparatus 1 further comprises a plurality of
individually controllable self-emissive contrast devices 4
configured to emit a plurality of beams. In an embodiment, the
self-emissive contrast device 4 is a radiation emitter, e.g. a
radiation emitting diode, such as a light emitting diode (LED), an
organic LED (OLED), a polymer LED (PLED), a fiber laser or a laser
diode (e.g., a solid state laser diode). In an embodiment, each of
the individually controllable elements 4 is a blue-violet laser
diode (e.g., Sanyo model no. DL-3146-151). Such diodes may be
supplied by companies such as Sanyo, Nichia, Osram, and Nitride. In
an embodiment, the diode emits UV radiation, e.g., having a
wavelength of about 365 nm or about 405 nm. In an embodiment, the
diode can provide an output power selected from the range of
0.5-250 mW, and optionally an output power of at least 50 mW. In an
embodiment the output power of a device 60, that may comprise a
self-emissive contrast device 4, is greater than 250 mW. In an
embodiment, the size of laser diode (naked die) is selected from
the range of 100-800 micrometers. In an embodiment, the laser diode
has an emission area selected from the range of 0.5-5 micrometers2.
In an embodiment, the laser diode has a divergence angle selected
from the range of 5-44 degrees. In an embodiment, the diodes have a
configuration (e.g., emission area, divergence angle, output power,
etc.) to provide a total brightness more than or equal to about
6.4.times.108 W/(m2sr).
[0038] The self-emissive contrast devices 4 are arranged on a frame
5 and may extend along the Y-direction and/or the X direction.
While one frame 5 is shown, the apparatus may have a plurality of
frames 5 as shown in FIG. 2. Further arranged on the frame 5 is
lens 12. Frame 5 and thus self-emissive contrast device 4 and lens
12 are substantially stationary in the X-Y plane. Frame 5,
self-emissive contrast device 4 and lens 12 may be moved in the
Z-direction by actuator 7. Alternatively or additionally, lens 12
may be moved in the Z-direction by an actuator related to this
particular lens. Optionally, each lens 12 may be provided with an
actuator.
[0039] The self-emissive contrast device 4 may be configured to
emit a beam and the projection system 12, 14 and 18 may be
configured to project the beam onto a target portion of, e.g., the
substrate. The self-emissive contrast device 4 and the projection
system form an optical column. The apparatus 1 may comprise an
actuator (e.g. motor 11) to move the optical column or a part
thereof with respect to the substrate. Frame 8 with arranged
thereon field lens 14 and imaging lens 18 may be rotatable with the
actuator. A combination of field lens 14 and imaging lens 18 forms
movable optics 9. In use, the frame 8 rotates about its own axis
10, for example, in the directions shown by the arrows in FIG. 2.
The frame 8 is rotated about the axis 10 using an actuator (e.g.
motor) 11. Further, the frame 8 may be moved in a Z direction by
motor 7 so that the movable optics 9 may be displaced relative to
the substrate table 2.
[0040] An aperture structure 13 having an aperture therein may be
located above lens 12 between the lens 12 and the self-emissive
contrast device 4. The aperture structure 13 can limit diffraction
effects of the lens 12, the associated self-emissive contrast
device 4 or of an adjacent lens 12 and a self-emissive contrast
device 4.
[0041] The depicted apparatus may be used by rotating the frame 8
and simultaneously moving the substrate on the substrate table 2
underneath the optical column. The self-emissive contrast device 4
can emit a beam through the lenses 12, 14, and 18 when the lenses
are substantially aligned with each other. By moving the lenses 14
and 18, the image of the beam on, e.g., the substrate is scanned
over a portion of the substrate. By simultaneously moving the
substrate on the substrate table 2 underneath the optical column,
the portion of the substrate 17, which is subjected to an image of
the self-emissive contrast device 4 is also moving. By switching
the self-emissive contrast device 4 "on" and "off" (e.g., having no
output or output below a threshold when it is "off" and having an
output above a threshold when it is "on") at high speed under
control of a controller, controlling the rotation of the optical
column or part thereof, controlling the intensity of the
self-emissive contrast device 4, and controlling the speed of the
substrate, a desired pattern can be imaged in the resist layer on
the substrate.
[0042] A controller 500 shown in FIG. 1 controls the overall
operations of the lithographic apparatus and in particular performs
a process described herein. Controller 500 can be embodied as a
suitably-programmed general purpose computer comprising a central
processing unit and volatile and/or non-volatile storage.
Optionally, the computer may include one or more input and output
devices such as a keyboard and screen, one or more network
connections and/or one or more interfaces to the various parts of
the lithographic apparatus. It will be appreciated that a
one-to-one relationship between controlling computer and
lithographic apparatus is not necessary. In an embodiment, one
computer can control multiple lithographic apparatuses. In an
embodiment, multiple networked computers can be used to control one
lithographic apparatus. The controller 500 may be configured to
control one or more associated process devices and/or substrate
handling devices in a lithocell or cluster of which the
lithographic apparatus forms a part. The controller 500 can be
configured to be subordinate to a supervisory control system of a
lithocell or cluster and/or an overall control system of a fab.
[0043] FIG. 2 depicts a schematic top view of the apparatus of FIG.
1 having self-emissive contrast devices 4. Like the apparatus 1
shown in FIG. 1, the apparatus 1 comprises a substrate table 2 to
hold a substrate 17, a positioning device 3 to move the substrate
table 2 in up to 6 degrees of freedom, an alignment/level sensor 19
to determine alignment between the self-emissive contrast device 4
and the substrate 17, and to determine whether the substrate 17 is
at level with respect to the projection of the self-emissive
contrast device 4. As depicted the substrate 17 has a rectangular
shape, however also or alternatively round substrates may be
processed.
[0044] The self-emissive contrast device 4 is arranged on a frame
15. The self-emissive contrast device 4 may be a radiation emitting
diode, e.g., a laser diode, for instance a blue-violet laser diode.
As shown in FIG. 2, the self-emissive contrast devices 4 may be
arranged into an array 21 extending in the X-Y plane.
[0045] The array 21 may be an elongate line. In an embodiment, the
array 21 may be a single dimensional array of self-emissive
contrast devices 4. In an embodiment, the array 21 may be a two
dimensional array of self-emissive contrast device 4.
[0046] A rotating frame 8 may be provided which may be rotating in
a direction depicted by the arrow. The rotating frame may be
provided with lenses 14, 18 (show in FIG. 1) to provide an image of
each of the self-emissive contrast devices 4. The apparatus may be
provided with an actuator to rotate the optical column comprising
the frame 8 and the lenses 14, 18 with respect to the
substrate.
[0047] FIG. 3 depicts a highly schematic, perspective view of the
rotating frame 8 provided with lenses 14, 18 at its perimeter. A
plurality of beams in this example 10 beams, are incident onto one
of the lenses and projected onto a target portion of, e.g., the
substrate 17 held by the substrate table 2. In an embodiment, the
plurality of beams is arranged in a straight line. The rotatable
frame is rotatable about axis 10 by means of an actuator (not
shown). As a result of the rotation of the rotatable frame 8, the
beams will be incident on successive lenses 14, 18 (field lens 14
and imaging lens 18) and will, incident on each successive lens, be
deflected thereby so as to travel along a part of the surface of
the substrate 17, as will be explained in more detail with
reference to FIG. 4. In an embodiment, each beam is generated by a
respective source, i.e. a self-emissive contrast device, e.g. a
laser diode (not shown in FIG. 3). In the arrangement depicted in
FIG. 3, the beams are deflected and brought together by a segmented
mirror 30 in order to reduce a distance between the beams, to
thereby enable a larger number of beams to be projected through the
same lens and to achieve resolution requirements to be discussed
below.
[0048] As the rotatable frame rotates, the beams are incident on
successive lenses. Each time a lens is irradiated by the beams, the
places where the beam is incident on a surface of the lens, moves.
Since the beams are projected on the target differently (with e.g.
a different deflection) depending on the place of incidence of the
beams on the lens, the beams (when reaching the target) will make a
scanning movement with each passage of a following lens. This
principle is further explained with reference to FIG. 4.
[0049] FIG. 4 depicts a highly schematic top view of a part of the
rotatable frame 8. A first set of beams is denoted by B1. A second
set of beams is denoted by B2. A third set of beams is denoted by
B3. Each set of beams is projected through a respective lens set
14, 18 of the rotatable frame 8. As the rotatable frame 8 rotates,
the beams B1 are projected onto the substrate 17 in a scanning
movement, thereby scanning area A14. Similarly, beams B2 scan area
A24 and beams B3 scan area A34. At the same time of the rotation of
the rotatable frame 8 by a corresponding actuator, the substrate 17
and substrate table are moved in the direction D. The direction D
may be along the X axis as depicted in FIG. 2. The direction D may
be substantially perpendicular to the scanning direction of the
beams in the areas A14, A24, A34.
[0050] As a result of the movement in direction D by a second
actuator (e.g. a movement of the substrate table by a corresponding
substrate table motor), successive scans of the beams when being
projected by successive lenses of the rotatable frame 8, are
projected so as to substantially abut each other. This results in
substantially abutting areas A11, A12, A13, A14 (areas A11, A12,
A13 being previously scanned and A14 being currently scanned as
shown in FIG. 4) for each successive scan of beams B1. Areas A21,
A22, A23 and A24 (areas A21, A22, A23 being previously scanned and
A24 being currently scanned as shown in FIG. 4) are for beams B2.
Areas A31, A32, A33 and A34 (areas A31, A32, A33 being previously
scanned and A34 being currently scanned as shown in FIG. 4) are for
beams B3. Thereby, the areas A1, A2 and A3 of the substrate surface
may be covered with a movement of the substrate in the direction D
while rotating the rotatable frame 8.
[0051] The projecting of multiple beams through a same lens allows
processing of a whole substrate in a shorter timeframe (at a same
rotating speed of the rotatable frame 8). This is because for each
passing of a lens, a plurality of beams scan the substrate 17 with
each lens. This allows increased displacement in the direction D
for successive scans. Viewed differently, for a given processing
time, the rotating speed of the rotatable frame may be reduced when
multiple beams are projected onto the substrate via a same lens.
This possibly reduces effects such as deformation of the rotatable
frame, wear, vibrations, turbulence, etc. due to high rotating
speed.
[0052] In an embodiment, the plurality of beams is arranged at an
angle to the tangent of the rotation of the lenses 14, 18 as shown
in FIG. 4. In an embodiment, the plurality of beams is arranged
such that each beam overlaps or abuts a scanning path of an
adjacent beam.
[0053] A further effect of the aspect that multiple beams are
projected at a time by the same lens may be found in relaxation of
tolerances. Due to tolerances of the lenses (positioning, optical
projection, etc), positions of successive areas A11, A12, A13, A14
(and/or of areas A21, A22, A23 and A24 and/or of areas A31, A32,
A33 and A34) may show some degree of positioning inaccuracy in
respect of each other. Therefore, some degree of overlap between
successive areas A11, A12, A13, A14 may be required. In case of for
example 10% of one beam as overlap, a processing speed would
thereby be reduced by a same factor of 10% in case of a single beam
at a time through a same lens. In a situation where there are 5 or
more beams projected through a same lens at a time, the same
overlap of 10% (similarly referring to one beam example above)
would be provided for every 5 or more projected lines, hence
reducing a total overlap by a factor of approximately 5 or more to
2% or less, thereby having a significantly lower effect on overall
processing speed. Similarly, projecting at least 10 beams may
reduce a total overlap by approximately a factor of 10. Thus,
effects of tolerances on processing time of a substrate may be
reduced by the feature that multiple beams are projected at a time
by the same lens. In addition or alternatively, more overlap (hence
a larger tolerance band) may be allowed, as the effects thereof on
processing are low given that multiple beams are projected at a
time by the same lens.
[0054] Alternatively or in addition to projecting multiple beams
via a same lens at a time, interlacing techniques could be used,
which however may require a comparably more stringent matching
between the lenses. Thus, the at least two beams projected onto the
substrate at a time via the same one of the lenses have a mutual
spacing, and the apparatus may be arranged to operate the second
actuator so as to move the substrate with respect to the optical
column to have a following projection of the beam to be projected
in the spacing.
[0055] In order to reduce a distance between successive beams in a
group in the direction D (thereby e.g. achieving a higher
resolution in the direction D), the beams may be arranged
diagonally in respect of each other, in respect of the direction D.
The spacing may be further reduced by providing a segmented mirror
30 in the optical path, each segment to reflect a respective one of
the beams, the segments being arranged so as to reduce a spacing
between the beams as reflected by the mirrors in respect of a
spacing between the beams as incident on the mirrors. Such effect
may also be achieved by a plurality of optical fibers. Each of the
beams is incident on a respective one of the fibers. The fibers are
arranged so as to reduce a spacing between the beams along an
optical path. As a result the beam spacing downstream of the
optical fibers is less than the beam spacing upstream of the
optical fibers.
[0056] Further, such effect may be achieved using an integrated
optical waveguide circuit having a plurality of inputs, each for
receiving a respective one of the beams. The integrated optical
waveguide circuit is arranged so as to reduce along an optical path
a spacing between the beams downstream of the integrated optical
waveguide circuit in respect of a spacing between the beams
upstream of the integrated optical waveguide circuit.
[0057] A system may be provided for controlling the focus of an
image projected onto a substrate. The arrangement may be provided
to adjust the focus of the image projected by part or all of an
optical column in an arrangement as discussed above.
[0058] In an embodiment the projection system projects the at least
one radiation beam onto a substrate formed from a layer of material
above the substrate 17 on which a device is to be formed so as to
cause local deposition of droplets of the material (e.g. metal) by
a laser induced material transfer.
[0059] Referring to FIG. 5, the physical mechanism of laser induced
material transfer is depicted. In an embodiment, a radiation beam
200 is focused through a substantially transparent material 202
(e.g., glass) at an intensity below the plasma breakdown of the
material 202. Surface heat absorption occurs on a substrate formed
from a donor material layer 204 (e.g., a metal film) overlying the
material 202. The heat absorption causes melting of the donor
material 204. Further, the heating causes an induced pressure
gradient in a forward direction leading to forward acceleration of
a donor material droplet 206 from the donor material layer 204 and
thus from the donor structure (e.g., plate) 208. Thus, the donor
material droplet 206 is released from the donor material layer 204
and is moved (with or without the aid of gravity) toward and onto
the substrate 17 on which a device is to be formed. By pointing the
beam 200 on the appropriate position on the donor plate 208, a
donor material pattern can be deposited on the substrate 17. In an
embodiment, the beam is focused on the donor material layer
204.
[0060] In an embodiment, one or more short pulses are used to cause
the transfer of the donor material. In an embodiment, the pulses
may be a few picoseconds or femto-seconds long to obtain quasi one
dimensional forward heat and mass transfer of molten material. Such
short pulses facilitate little to no lateral heat flow in the
material layer 204 and thus little or no thermal load on the donor
structure 208. The short pulses enable rapid melting and forward
acceleration of the material (e.g., vaporized material, such as
metal, would lose its forward directionality leading to a
splattering deposition). The short pulses enable heating of the
material to just above the heating temperature but below the
vaporization temperature. For example, for aluminum, a temperature
of about 900 to 1000 degrees Celsius is desirable.
[0061] In an embodiment, through the use of a laser pulse, an
amount of material (e.g., metal) is transferred from the donor
structure 208 to the substrate 17 in the form of 100-1000 nm
droplets. In an embodiment, the donor material comprises or
consists essentially of a metal. In an embodiment, the metal is
aluminum. In an embodiment, the material layer 204 is in the form a
film. In an embodiment, the film is attached to another body or
layer. As discussed above, the body or layer may be a glass.
[0062] FIG. 1 depicts an embodiment of the invention. The
lithographic apparatus 1 comprises a projection system 50 that
comprises a stationary part and a moving part. The projection
system may comprise lenses 12, 14 and 18 as depicted in FIG. 1, for
example. The projection system 50 is configured to project a
plurality of radiation beams onto locations on a substrate 17. The
locations are selected based on a pattern. The pattern is to be
formed on the substrate 17. In an embodiment the pattern is formed
in a layer of photoresist material. In an embodiment the pattern is
formed in a layer of donor material, which subsequently forms a
corresponding pattern in a layer of a device.
[0063] FIG. 1 depicts a frame 8 that rotates about the axis 10
during use of the apparatus 1. The frame 8 can deform as a result
of its rotation or translation. For example, one or more parts of
the frame 8 can expand in the radial direction as a result of the
rotation. One or more other pieces of rotating or moving equipment
in the apparatus 1 may also deform as a result of its respective
rotation or other movement.
[0064] The frame 8 of FIG. 1 may be configured to hold at least one
field lens 14 and at least one imaging lens 18. It is desirable for
these lenses to be positioned accurately with respect to each other
and with respect to the apparatus 1 in order to improve the imaging
accuracy of the apparatus 1.
[0065] In particular, in one printing method in which the apparatus
1 can be used, each swipe of the radiation spot brush generates a
pattern of lines instead of a continuous band. A subsequent swipe
of the radiation spot brush is timed such that it fills in (part
of) the spaces between lines written in a previous swipe(s).
Repeating this action and properly timing the switching "on" and
"off" of the self-emissive contrast devices 4 and movement of the
target (e.g., substrate 17) results in a continuously filled
surface on the substrate 17. This printing method is called
interlaced printing.
[0066] In interlaced printing, each line should be placed (i.e.
printed) with respect to its neighbor with high precision. In this
case, high precision means to within 100 nm, for example. The
position at which each line is printed on the target is directly
related to the positioning of the lenses 14, 18 on the frame 8. As
such, these lenses 14, 18 are desirably placed on the frame 8 with
an accuracy of within, e.g., 100 nm. Mechanically this is extremely
challenging, in particular due to the centripetal forces exerted on
the lenses 14, 18 during operation, in addition to manufacturing
tolerances.
[0067] It is desirable, for example, to provide a apparatus 1 in
which the lenses 14, 18 are positioned more accurately with respect
to each other and with respect to the apparatus 1 during movement
of the frame 8. It is desirable to reduce the constraint as to how
accurately the lenses 14, 18 are positioned with respect to each
other and with respect to the apparatus 1.
[0068] FIG. 6 depicts a frame 8 according to an embodiment of the
present invention. The section of FIG. 6 to the left of the axis 10
depicts a cross-sectional view of the frame 8 at rest. The section
of FIG. 6 to the right of the axis 10 depicts an external view of
the frame 8 during rotation.
[0069] In an embodiment the frame 8 comprises a shaft 70 and a
flange 62. The flange 62 extends radially outwards at an angle
.alpha. relative to the axis 10. The flange 62 is configured to
hold at least one lens 14, 18. The at least one lens may be, for
example, a field lens 14 or an imaging lens 18.
[0070] In an embodiment the frame 8 is configured such that the
angle .alpha. at which the flange extends is substantially constant
over a continuous range of rotational speeds. Here, substantially
constant means that the angle .alpha. changes by at most 1 mrad,
for example. The direction of rotation is irrelevant.
[0071] As mentioned above, rotating equipment expands in the radial
direction as a result of rotation. The amount of expansion is
determined, in part, by the rotational speed and the radius of the
piece of equipment. As shown in FIG. 6, the radius of the frame 8
varies over the height (in the Z direction) of the frame 8. For
example, the flange 62 has an outer radius R1 that is greater than
an outer radius R3 of the shaft 70 (see FIG. 7).
[0072] As a result, some sections of the frame 8 are subject to a
greater expansion stress than other sections of the frame 8. The
difference in expansion stress across the frame 8 introduces a
deflection, or tilt, of the frame 8. In the case of the flange 62,
the deflection can result in the angle .alpha. at which the flange
62 extends varying as the rotational speed of the frame 8 varies.
This is depicted schematically in FIG. 6.
[0073] In the right hand section of FIG. 6, the flange 64 undergoes
a deflection when the frame 8 rotates. The left hand side of FIG. 6
shows that at rest (i.e. a rotation speed of 0), the flange 64
extends at an angle .beta. with respect to the axis 10 wherein the
angle .beta. is about 90 degrees. The right hand side of FIG. 6
shows that when the frame 8 rotates, the frame 8 undergoes a
deflection such that the flange 64 extends at an angle of 90
degrees minus 0 with respect the axis 10. Such a deflection will
undesirably change the position at which the lens 18 held by the
flange 64 focuses a radiation beam onto the target.
[0074] By configuring the frame 8 such that the angle .alpha. at
which the flange 62 extends is substantially constant over a
continuous range of rotational speeds, deflection of the frame 8 is
reduced. As a result, the focusing of radiation beams performed by
the at least one lens 14, 18 held by the flange 62 is more
consistent as the rotational speed of the frame 8 varies.
[0075] Rotation of the frame 8 may cause the radius of the frame 8
at a particular point to change by from about 50 .mu.m to about 100
.mu.m at a rotational speed of about 80 Hz. These values are for a
frame 8 made from steel. In general, the greater the rotational
speed of the frame 8, the greater the expansion of the radius of
the frame 8. For example, if the rotational speed is about 140 Hz,
then the change in radius of a particular point on the frame 8 may
be of the order of from about 150 .mu.m to about 300 .mu.m (i.e.
three times as great as for a rotational speed of 80 Hz). The
variation in radius across the frame 8 can result in a deflection
tilt of from about 0.5 mrad to about 5 mrad for a rotational speed
of 80 Hz, or from about 1.5 mrad to about 15 mrad for a rotation
speed of about 140 Hz.
[0076] Hence, in an embodiment, there is provided a system in which
the variation in rotational speed of the frame 8 results in a
deflection tilt which is reduced compared to the art. In an
embodiment, the frame 8 is configured such that the angle .alpha.
at which the flange 62 extends varies by upmost 1 mrad over the
continuous range of rotational speeds. In an embodiment, the angle
.alpha. varies by at most about 0.5 mrad, and optionally by at most
about 0.1 mrad over the continuous range of rotational speeds.
[0077] In an embodiment, the continuous range of rotational speeds
has a lower limit of 0. Hence, the angle .alpha. at which the
flange 62 extends remains substantially constant from when the
frame 8 is at rest to when the frame 8 rotates at the upper limit
of the continuous range of rotational speeds. In an embodiment the
continuous range of rotational speeds has an upper limit of at
least 80 Hz, optionally at least 100 Hz, and optionally at least
140 Hz. The continuous range of rotational speeds is not
particularly limited and may have an upper limit of 200 Hz or
higher.
[0078] By the frame 8 not having a constant radius across its full
height (in the Z direction), the frame 8 can have a relatively low
weight. This can increase safety during an emergency stop of the
frame 8 and means that the frame 8 should require a lesser amount
of energy in order to speed up.
[0079] There are various ways of configuring the frame 8 such that
the angle .alpha. at which the flange 62 extends is substantially
constant over a continuous range of rotational speeds. As depicted
in FIG. 6, the frame 8 may comprise a symmetric design in which the
flange 62 undergoes a moment due to the shaft 70 on either side of
the flange 62, wherein the two moments cancel each other out. In an
embodiment, the angle .alpha. is substantially a right angle. In
this case, the at least one lens 14, 18 may be positioned
substantially in the plane of the flange 62. However, the flange 62
may extend relative to the axis 10 at an angle different from a
right angle, for example at 85 degrees.
[0080] The deflection tilt of the flange 62 can be considered to be
the result of a moment exerted on the flange 62 by the shaft 70. In
general, the shaft 70 may have a smaller radius than the flange 62.
As depicted in FIG. 6, as the shaft 70 expands, the lower section
63 of the shaft 70 may tilt about a hinge point 91. Of course, the
hinge point 91 is in fact an annulus that extends around the axis
10, rather than being a single point. This results in the lower
section 63 of the shaft 70 exerting a moment on the flange 64, thus
causing the flange 64 to deflect, or tilt, as shown in the right
hand section of FIG. 6.
[0081] In the symmetric design of FIG. 6, the moment exerted on the
flange 62 by the upper section 61 of the shaft 70 substantially
equals and opposes the moment exerted on the flange 62 by the lower
section 63 of the shaft 70.
[0082] As a result, the shaft 70 exerts substantially no overall
moment about an axis perpendicular to the axis 10 of rotation, on
the flange 62. The deflection of flange 64 is shown in FIG. 6
merely for comparison with the non-deflected flange 62.
[0083] One way to help ensure that the upper section 61 and the
lower section 63 of the shaft 70 exert substantially equal and
opposing moments on the flange 62 is to have the cross-section of
the upper section 61 correspond to the cross-section of the lower
section 63 of the shaft 70. However, in an embodiment, a
cross-section of the upper section 61 is different from a
cross-section of the lower section 63 of the shaft. This is
depicted, for example, in FIG. 6.
[0084] The moment exerted on the flange by the shaft 70 is given by
the equation (1) below:
M flange = G .DELTA. R .DELTA. z .DELTA. z = t f .DELTA. P 2 ( R 1
2 - R 0 2 ) z .infin. flange z ( 1 ) ##EQU00001##
[0085] G represents the shear modulus of the frame 8. AR represents
the difference in radius of the frame 8 between different points
along the vertical extent of the frame 8. In particular delta R
equals .DELTA.Rz=i-.DELTA.Rz=i-1. .DELTA.P represents the
"infinitely small" angle portion (in radians) of the frame 8. This
allows the axisymmetric frame 8 to be considered as a
two-dimensional problem. R1 represents the outer radius of the
shaft 70. R0 represents the inner radius of the shaft 70. And, z
represents the vertical coordinate along the axis 10 of rotation of
the frame 8.
[0086] As depicted in FIG. 6, in an embodiment, the frame 8
comprises a hole 66 along the axis 10 of rotation. The hole 66 may
be provided to allow for space for an actuator and/or a bearing,
for example. However, the hole 66 may not be present in an
embodiment. In this case, the actuator and/or bearing may be
positioned outside of the frame 8.
[0087] FIG. 7 depicts schematically a frame 8 according to an
embodiment of the invention. In each of FIGS. 7 to 12, the
cross-sectional shape of one half of the frame 8 is depicted. In an
embodiment the frame 8 has a shape that is substantially circularly
symmetric about the axis 10.
[0088] In the embodiment depicted in FIG. 7, a section of the shaft
70 on one side, in the axial direction, of the flange 62 exerts
substantially no moment on the flange 62. In this case, it is not
necessary to balance the moment exerted on the flange 62 by a
corresponding section of the shaft 70 on the opposite side of the
flange 62 (in the axial direction). This is because the shaft 70 on
one side of the flange 62 exerts substantially no moment on the
flange 62.
[0089] One way to achieve the section of the shaft 70 exerting
substantially no moment on the flange 62 is to choose the inner and
outer radii of the flange 62 and the shaft 70 such that a product
of the inner radius R0 of the flange 62 and the outer radius R1 of
the flange 62 is substantially equal to the product of the inner
radius R2 of the shaft 70 and the outer radius R3 of the shaft 70.
It is desirable that R0R1=R2R3.
[0090] Exact equality of the products of the inner and outer radii
of the flange 62 and the shaft 70 is not necessary. For example,
the product ROR1 may differ from the product R2R3 by at most 20%,
by at most 10%, or by at most 5%. In particular, if the product
ROR1 is within 10% of the product R2R3, then there may be a
significant reduction in deflection of the flange 62 such that the
flange 62 extends at an angle .alpha. that is substantially
constant as the rotational speed of the frame 8 varies for
rotational speeds of up to about 140 Hz. Apart from the section of
the shaft 70 that is adjacent to the flange 62, the remainder of
the shaft 70 has an influence on the flange 62. Hence, for some
parts of the shaft 70, there may be significant deviation from the
equality R0R1=R2R3. However, the section of the shaft 70 adjacent
to the flange 62 has the greatest influence on the flange 62.
[0091] In the case that there is no hole 66 in the frame 8, the
equality R0R1=R2R3 is trivially satisfied. However, in this case
(i.e. there is no hole 66 in the frame 8), it is desirable that the
outer radius R1 of the flange 62 is substantially equal to the
outer radius R3 of the shaft 70 such that the shaft 70 and the
flange 62 expand by substantially the same amount such that there
is substantially no overall deflection.
[0092] By providing compatible radii that satisfy R0R1=R2R3 (to
within .+-.10%), similar expansion stresses are exerted at the
cross-section where the flange 62 and the shaft 70 intersect. As
such, there is loading equilibrium between the flange 62 and the
shaft 70, thus resulting in substantially no deflection of the
flange 62 as a result of the shaft 70.
[0093] FIGS. 8, 9 and 10 each depict an embodiment in which the
flange 62 is at least partially decoupled from a moment exerted by
the shaft 70. In an embodiment the flange 62 is connected to the
shaft 70 by a connecter 80, 90 that is more flexible than the
flange 62. For example, the connector 80, 90 may be thinner than
the flange 62.
[0094] By at least partially decoupling the flange 62 from a moment
exerted by the shaft 70, the deflection of the flange 62 as a
result of the shaft 70 is decreased. This helps improve the
accuracy of the focal plane of the lens 14, 18 held by the flange
62 during rotation of the frame 8.
[0095] FIG. 8 depicts an embodiment in which the flange 62 is
connected to the shaft 70 by a connector 80, which takes the form
of a membrane. When the shaft 70 variously tilts with respect to
the axis 10 over the continuous range of rotational speeds, the
connector 80 flexes such that the angle .alpha. at which the flange
62 extends is substantially constant.
[0096] As the rotational speed of the frame 8 varies, the shaft 70
variously tilts with respect to the axis 10. As depicted in FIG. 8,
the shaft 70 may tilt or deflect relative to the axis 10 of
rotation about the hinge point 91. As mentioned above, the point 91
is in fact an annulus that extends around the axis 10 of rotation,
rather than being a specific point. In FIG. 8 (as well as in FIGS.
9 to 10) the dashed lines represent the position of the frame 8
when the frame 8 is rotating. The angle of extension of the flange
62 is substantially constant for when the frame 8 is at rest (shown
in black lines in FIGS. 8 to 10) and when the frame 8 is rotating
(shown in dashed lines in FIGS. 8 to 10).
[0097] As depicted in FIG. 9, in an embodiment connector 90 extends
from its connection (at hinge point 92) to the shaft 70 towards the
middle 94, in the axial direction, of the shaft 70. In this
embodiment, the flange 62 imposes a moment onto the shaft 70, the
moment causing a deflection of the shaft 70 about the hinge point
91. An additional moment is imposed, having its center of rotation
at the hinge point 92. As such, the frame 8 may be designed for
reduced flange deflection. In an embodiment, the additional moment
results in a deflection of the flange 62 that opposes and
substantially equals the deflection about the hinge point 91. As
depicted in FIG. 9, in an embodiment the connector 90 is connected
to the flange 62 at a position closer to the middle 94, in the
axial direction, of the shaft 70 than a position 92 at which the
connector 90 is connected to the shaft 70.
[0098] FIG. 10 depicts an embodiment in which the connector
comprises a flange connection section 95 that extends from its
connection to the flange 62 towards the middle 94 in the axial
direction, of the shaft 70. The purpose of the flange connection
section 95 is to reduce vertical displacement of the flange 62
during rotation of the frame 8. The flange 62 produces an
additional moment, having its center of rotation at the hinge point
93 shown in FIG. 10.
[0099] In an embodiment, when the shaft 70 variously tilts with
respect to the axis 10 over the continuous range of rotational
speeds, the connector 80, 90 flexes such that the position, along
the axis 10, of the flange 62 is substantially constant. This helps
to reduce the effect of the rotation of the frame 8 on the vertical
position of the flange 62, and therefore on the focusing provided
by the lens 14, 18 held by the flange 62.
[0100] In an embodiment the flange connection section 95 and/or the
connector 90 have a thickness that decreases gradually from
radially inwards to radially outwards. In an embodiment the flange
connection section 95 and the connector 90 have a saw-tooth shape
as depicted in FIG. 10.
[0101] FIG. 11 depicts schematically a part of a frame 8 according
to an embodiment of the present invention. In FIGS. 11 and 12, the
solid black lines depict the position of the frame 8 at rest. The
dashed lines represent the position of the frame 8 when the frame 8
is rotating about the axis 10.
[0102] When the frame 8 rotates, the flange 62 imposes a moment on
the shaft 70. This causes the shaft 70 to tilt or deflect about the
hinge point 91. In order to compensate for the resulting tilt or
deflection on the flange 62, the flange 62 comprises a recess 110
on a surface of the flange 62 that faces the middle 94, in the
axial direction, of the shaft 70.
[0103] In an embodiment, the recess 110 is a continuous recess that
extends around the axis 10. However, for example, the recess 110
may comprise a series of recesses or depressions with
discontinuities in between. In an embodiment the recess 110 is
substantially circular and concentric with the frame 8.
[0104] The recess 110 partially separates the peripheral part of
the flange 62 from the rest of the frame 8. The recess 110
introduces a non-symmetric suspension of the partially separated
periphery of the flange 62. As a result, this peripheral part
introduces a moment, which counteracts the original flange
deflection. As depicted in FIG. 11, this moment results in the
peripheral part of the flange 62 deflecting, or tilting, about the
hinge point 111. As a result of the recess 110, the hinge point 111
of deflection is lower than would otherwise be the case.
[0105] FIG. 12 depicts an embodiment of the invention. As depicted
in FIG. 12, the flange 62 comprises a protruding rim 120 on a
surface of the flange 62 that faces the middle 94, in the axial
direction, of the shaft 70. The protruding rim 120 imposes a moment
onto the connection between the flange 62 and the shaft 70. One way
to view this is to consider that the protruding rim 120 "wants to"
expand more than the flange 62 allows it to.
[0106] By providing the protruding rim 120 that imposes a counter
moment, the original flange deflection is at least partly
counteracted by the presence of the protruding rim 120. By
selecting the dimensions of the protruding rim 120, the original
flange deflection can be counteracted such that the peripheral part
of the flange 62 remains at the substantially same angle with
respect to the axis 10 of rotation regardless of the rotational
speed of the frame 8.
[0107] In an embodiment the lens 14, 18 held by the flange 62 is
held at the peripheral part of the flange 62. As such, the lens 14,
18 remains at a substantially constant angle regardless of the
speed of rotation of the frame 8.
[0108] In an embodiment the protruding rim 120 is a continuous
protruding rim 120 that extends around the axis 10 of rotation of
the frame 8. However, for example, in an embodiment the protruding
rim 120 comprises discontinuities. The protruding rim 120 may
comprise a plurality of protrusions, which may or may not be
elongate. In an embodiment the protruding rim 120 is substantially
circular and concentric with the frame 8.
[0109] If a rim or recess is positioned on the opposing surface of
the flange 62, i.e. on the surface that faces away from the middle
94 of the shaft 70, then the rim or recess would result in an
increased tilt or deflection of the flange 62.
[0110] In an embodiment, a monolithic component comprises the
connector 80, 90, the flange 62 and the shaft 70. The frame 8 may
be made from steel, for example. However, other suitable materials
may also be used. In an embodiment, the frame 8 is an assembly of
separate components corresponding to the shaft 70, the connector
80, 90 and the flange 62. In an embodiment the frame 8 is "solid",
which means that there is no hole 66 along the axis 10 of rotation.
The frame 8 may be monolithic or assembled from various parts.
[0111] In an embodiment the frame 8 comprises a second flange 64.
For example, in an embodiment, the flange 62 holds at least one
field lens 14. Or, in an embodiment, the second flange 64 holds at
least one imaging lens 18. In an embodiment the frame 8 is
configured such that an angle .beta. at which the second flange
extends is substantially constant over a continuous range of
rotational speeds.
[0112] An embodiment of the present invention makes it possible to
at least partially compensate, or prevent, unwanted flange
deflection. Flange deflection can otherwise result in misaligned
optics in the apparatus 1. An embodiment of the present invention
can be used to provide a frame 8 that can be used over a range of
angular velocities, while retaining aligned optics. An embodiment
of the present invention may not require any calibration or
interface adjustment in order to make the optics aligned for a
particular angle of velocity.
[0113] The frame 8 can be designed to be robust. The frame 8 can be
manufactured relatively easily and inexpensively because, for
example, it may not require moving parts and may not require large
extra components that would increase the weight of the frame 8.
[0114] FIG. 13 depicts an embodiment of the present invention. FIG.
13 depicts a projection system 50 configured to project a radiation
beam (or a plurality of radiation beams) onto a target (e.g.,
substrate 17). In an embodiment the projection system 50 comprises
a frame 8 and a stationary part 130.
[0115] The frame 8 is configured to rotate about an axis 10
defining a tangential direction and a radial direction. For
example, the radial direction extends radially outwards from the
axis 10. The radial direction is perpendicular to the axis 10. The
tangential direction is perpendicular to the radial direction and
is in a plane perpendicular to the axis 10.
[0116] In an embodiment the frame 8 holds at least one lens 141
that moves with movement of the frame. The lens 141 is configured
to focus the radiation beam in only the tangential or the radial
direction.
[0117] In an embodiment the stationary part 130 comprises at least
one substantially stationary lens 142. The substantially stationary
lens 142 is configured to focus the radiation in only the other of
the tangential or radial direction. The stationary part 130 is
stationary with respect to the apparatus 1.
[0118] Hence, the functions of focusing the radiation beam in the
tangential direction and the radial direction are divided between
the lens 141 and the substantially stationary lens 142. This is
different from other systems in which the lens held by the frame
performs the functions of focusing the radiation beam in both the
tangential direction and the radial direction.
[0119] According to an embodiment of the present invention, the
substantially stationary lens 142 fully determines either the
tangential position or the radial position of the radiation beam on
the target. As a result, this aspect of the position of the
radiation beam on the target is not affected by the position of the
lens 141 held by the frame 8. Any movement of the lens 141 as the
rotational speed of the frame 8 varies does not affect the aspect
of the position of the radiation beam on the target that is fully
determined by the substantially stationary lens 142.
[0120] In an embodiment the lens 141 is configured to focus the
radiation beam in the tangential direction, and the substantially
stationary lens 142 is configured to focus the radiation beam in
the radial direction. The radial positioning of the radiation beam
determines the position of lines drawn by the radiation beam on the
target. In the system of interlaced printing mentioned above, the
lines are placed to a very high accuracy, for example within 100
nm. By providing the substantially stationary lens 142 that focuses
the radiation beam in the radial direction, the radial position of
the radiation beam on the target is not substantially affected by
the radial position of the lens 141 in the frame 8. Hence, the
accuracy of positioning of the radiation beams on the target is
improved. This makes interlaced printing more feasible.
[0121] By performing interlaced printing, it may not be necessary
to provide the apparatus 1 with a pitch converter to narrow the
pitch of the radiation beams focused by different lenses 141 in the
frame 8. This is because in interlaced printing, the pitch can be
relatively large, with subsequent patterns of lines interlacing in
the gaps so as to form a continuous pattern on the target.
[0122] In an embodiment the lens 141 magnifies the radiation beam
at a magnification, and the substantially stationary lens 142
magnifies the radiation beam at the same magnification. The
magnification in the tangential and radial directions is affected
by the position and the focal length of each of the lens 141 and
the substantially stationary lens 142. In particular, the position
of the lenses along the optical path affects the magnification. By
selecting the positions and the focal lengths of the lenses, the
magnification in the tangential and radial directions can be made
substantially equal. However, in an embodiment, the magnification
in the tangential direction is different from the magnification in
the radial direction. This may be desirable, for example, if the
self-emissive contrast device 4 comprises an elliptical source. In
this case, by having a different magnification in the tangential
and radial directions, the elliptical source can be compensated
for.
[0123] In an embodiment the lens 141 is a field lens 141. In an
embodiment the frame 8 holds at least one imaging lens 181 axially
spaced from the field lens 141. The frame 8 may comprise two
flanges 62, 64. The flange 62 may hold the field lens 141. The
flange 64 may hold the imaging lens 181.
[0124] In an embodiment, the frame 8 holds at least 100 field
lenses 141 and/or at least 100 imaging lenses 181. For example,
there may be in the range of from about 120 to about 150 of each of
the field lenses 141 and/or imaging lenses 181 held in the frame 8.
As such, the width of each of the lenses 141, 181 is limited by the
size of the frame 8.
[0125] The free working distance is determined by the numerical
aperture (NA) and the width of the lens. A longer free working
distance is desirable. The larger the width of a lens, the longer
the free working distance. The substantially stationary lenses 142,
182 can be made to have a greater width than the lenses 141, 181,
because the substantially stationary lenses 142, 182 do not have
the same width restriction as the lenses 141, 181. Accordingly, the
substantially stationary lenses 142, 182 can have a larger free
working distance than the lenses 141, 181. An embodiment of the
present invention allows the design area for the optics of the
apparatus 1 to be enlarged. An apparatus 1 according to an
embodiment of the present invention may not require a pitch
converter to convert to a very small pitch.
[0126] In an embodiment the projection system 50 comprises at least
two substantially stationary lenses 142, 182 axially spaced from
each other. For example, there may be at least one substantially
stationary lens 142 that pairs with the field lens 141 so as to
together provide for field focusing in the tangential and radial
directions. Another substantially stationary lens 182 may combine
with the imaging lens 181 to focus in both the tangential and
radial directions in the imaging plane.
[0127] FIG. 14 depicts an embodiment of the invention. As depicted
in FIG. 14, in an embodiment the at least two substantially
stationary lenses 142, 182 are disposed between, in the axial
direction, the at least one field lens 141 and the at least one
imaging lens 181.
[0128] FIG. 15 depicts an embodiment in which each of the at least
one field lens 141 and the at least one imaging lens 181 are
disposed optically downstream, in the axial direction, of a
respective one of the at least two substantially stationary lenses
142, 182.
[0129] The embodiments depicted in FIGS. 14 and 15 provide the
greatest overall free working distance of the optical system. This
is a particular advantage of the embodiments depicted in FIGS. 14
and 15.
[0130] FIG. 16 depicts an embodiment in which the at least one
field lens 141 and the at least one imaging lens 181 are disposed
between, in the axial direction, the at least two substantially
stationary lenses 142, 182.
[0131] By positioning both substantially stationary lenses 142, 182
outside of the frame 8, the projection system 50 of FIG. 16 is
relatively easy to manufacture and maintain. Hence, the embodiment
depicted in FIG. 16 is mechanically advantageous.
[0132] FIG. 17 depicts an embodiment in which each of the at least
one field lens 141 and the at least one imaging lens 181 are
disposed optically upstream, in the axial direction, of a
respective one of the at least two substantially stationary lenses
142, 182.
[0133] FIG. 18 depicts, in plan view, a substantially stationary
lens 142 and a plurality of moving lenses 141. As depicted in FIG.
18, in an embodiment the substantially stationary lens 142 is made
out of a single piece. In other words, the substantially stationary
lens 142 may be monolithic. In an embodiment the substantially
stationary lens 142 extends in the tangential direction of the
frame 8. In an embodiment the substantially stationary lens 142 has
a curved shape that corresponds to the tangential direction of the
frame 8. This is depicted, for example, in FIG. 18.
[0134] However, this need not necessarily be the case. For example,
as depicted in FIG. 19 in an embodiment the substantially
stationary lens 142 is built up out of overlapping segments. In an
embodiment the substantially stationary lens 142 comprises a
plurality of overlapping, in the tangential direction,
substantially stationary sub-lenses 1421. Here the term overlapping
in the tangential direction means that when viewing the
substantially stationary lens 142 along the radial direction, the
substantially stationary lens appears to be continuous.
[0135] In an embodiment each of the plurality of substantially
stationary sub-lenses 1421 is straight. However, in an embodiment
at least one of the substantially stationary sub-lenses 1421 is
curved. In particular the curve may follow the tangential direction
of the frame 8.
[0136] FIG. 20 depicts an embodiment in which the connector
comprises a flange connection section 95 that extends from its
connection to the flange 62 towards the middle 94 in the axial
direction, of the shaft 70. In an embodiment the connector 90 is
connected to the shaft 70 at a position closer to the middle 94, in
the axial direction, of the shaft 70 than a position 92 at which
the connector 90 is connected to the flange 62.
[0137] The connector comprises a protrusion 201. In an embodiment
the protrusion 201 is located at the `hinge` point of the connector
90. The centrifugal force of the protrusion 201 helps ensure that
the connector is straightened during rotation of the frame 8. This
results in less deformation at the tip of the flange 62. The
connector 90 may be formed of one piece of material, or by several
parts attached to each other. For example in an embodiment the
protrusion 201 is formed of a separate piece of material from the
remainder of the connector 90. In an embodiment the protrusion is
formed of a material that has a higher density than the rest of the
connector 90.
[0138] In an embodiment the at least one lens 141, 181 comprises a
cylinder lens. A cylinder lens is suitable for focusing the
radiation beam in only one of the tangential or radial direction.
Other types of lenses suitable for performing this function may be
used.
[0139] In an embodiment the substantially stationary lens 142, 182
comprises a cylinder lens. In an embodiment, the lens 141, 181
extends in the radial direction. This is depicted in FIGS. 18 and
19, for example.
[0140] An embodiment of the present invention may allow the number
of self-emissive contrast devices 4 to be reduced by, for example,
almost 40% by arranging the self-emissive contrast devices 4 in a
more optimized layout.
[0141] An embodiment of the present invention may allow for more
accurate positioning of radiation beams because the positioning in
the radial direction can be manipulated by the laser-firing timing
(i.e. the timing at which the self-emissive contrast devices 4 are
turned on and off), and the tangential positioning is fixed by
substantially stationary optics which can be adjusted if
needed.
[0142] An embodiment of the present invention enables interlaced
printing. This results in less sensitivity to local disturbances
due to the integrating nature with respect to disturbances.
[0143] In accordance with a device manufacturing method, a device,
such as a display, integrated circuit or any other item may be
manufactured from the substrate on which the pattern has been
projected.
[0144] Although specific reference may be made in this text to the
use of lithographic or exposure apparatus in the manufacture of
ICs, it should be understood that the lithographic or exposure
apparatus described herein may have other applications, such as the
manufacture of integrated optical systems, guidance and detection
patterns for magnetic domain memories, flat-panel displays,
liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The
skilled artisan will appreciate that, in the context of such
alternative applications, any use of the terms "wafer" or "die"
herein may be considered as synonymous with the more general terms
"substrate" or "target portion", respectively. The substrate
referred to herein may be processed, before or after exposure, in
for example a track (a tool that typically applies a layer of
resist to a substrate and develops the exposed resist), a metrology
tool and/or an inspection tool. Where applicable, the disclosure
herein may be applied to such and other substrate processing tools.
Further, the substrate may be processed more than once, for example
in order to create a multi-layer IC, so that the term substrate
used herein may also refer to a substrate that already contains
multiple processed layers.
[0145] The term "lens", where the context allows, may refer to any
one of various types of optical components, including refractive,
diffractive, reflective, magnetic, electromagnetic and
electrostatic optical components or combinations thereof.
[0146] The descriptions above are intended to be illustrative, not
limiting. Thus, it will be apparent to one skilled in the art that
modifications may be made to the invention as described without
departing from the scope of the claims set out below.
* * * * *